The present invention relates to an injector device for containers of syringe type, comprising a barrel of axially roughly constant cross-section, a front opening and at least one movable wall inserted in the barrel for displacement of a container content, the injector comprising a) a housing or housing part arranged to receive the container at least axially stationary, b) an integral or composite piston rod arrangement operable to displace the container movable wall at least in the forward direction and c) a track system for controlling or sequencing the piston rod movements, the track system comprising at least one cooperating track and follower, the cooperating track and follower being arranged stationary with respect to the housing and the piston rod respectively, or vice versa, and in cooperation allowing at least one forward for the piston rod. The invention also relates to a method for operating such a device.
Although simple in principle injection procedures based on syringe type devices with injection needles require mastering of several discrete steps. Before the mere injection procedure some initiation actions may be required. Filling the syringe with medication withdrawn from a reservoir such as a vial may be needed, taking into account the proper dose to be administered. In order to avoid this step in the actual treatment situation it is common to provide pre-filled syringes, in which case, however, a dose setting or selecting step may be needed. In its first movement the syringe piston may need an extraordinary break-loose force after storage to overcome both internal reshaping resistance and an increased wall friction due to adherence or depletion of lubricant in contact points. For storage and shelf life reasons pre-filled syringes sometimes are delivered in dual or multiple-chamber form, requiring an additional mixing step immediately before treatment. De-aeration and pre-ejection are generally needed to remove gas in the vessel compartment and fill out spaces for example at the front sealing, outlet attachments and the interior of the outlet devices or needles. Syringes containing multiple doses further requires repeated ejection of predetermined volumes under avoidance of both over and under dosing, overdosing generally being irreversible and under-dosing often being undetected or unavoidable when ejecting an insufficient last dose from the syringe. Proper sequencing of all these steps are crucial to a safe and non-traumatic treatment.
These demands can be met also when using the simplest injection devices, such as the common hypodermic syringe, when in the hands of a skilled operator who also may initiate medically relevant corrective measures in case of accidents and malfunction. However, a general treatment trend is to place administration responsibility on the patients themselves, also in the case of child, elderly and disabled persons. In long-term treatment the patient often develop a certain skill but less frequent administration schemes also exist, often including situations of emergency or patient imbalance. Other unique problems in patient selfadministration, as compared to assistant operated administration, is that less suitable and often strained body positions are required and that apprehended or experienced pain or discomfort may interfere with the medically desirable action pattern. In summary, especially the selfadministration requires more sophisticated devices to facilitate the injection procedure and avoid or reduce risks for mistakes. Patients dependent on daily or occasional administrations also have a legitimate need for convenience and devices discrete enough to be brought around in daily life. Yet it is desirable that such sophistication and convenience is kept simple and inexpensive to allow for widespread distribution and inclusion also in disposable devices.
Various proposals have been put forward for injector devices assisting the user in many of the steps outlined. While meritorious in some respects none seem to deal with more than part of the total sequence. The U.S. Pat. No. 5,244,465 describes limiting arrangements for securing a single ejection of one of several selectable dose volumes. The U.S. Pat. No. 4,050,459, GB 1230522 and DE G8509572 specifications describe various trail for securing repeated multiple equal doses of predetermined volume. The U.S. Pat. Nos. 3,517,668 and 5,807,346 and the PCT/CH96/00115 application describe arrangements for multiple ejections of selectable dose volumes. The U.S. Pat. No. 4,832,694 describes a trail arrangement for a single aspiration and ejection cycle under prevention of any reverse movement. The specifications referred to do not give any solutions to the earlier phases in injection sequence or how to integrate such phases. The U.S. Pat. Nos. 4,968,299, 4,874,381, 5,080,649 and 5,728,075 and WO 93/14799 all relates to arrangements for securing mixing of contents in two chamber syringes followed by injection, utilizing a screw-threaded mechanism for the mixing phase. Again these suggestions only relate to a part of the overall operation.
Accordingly there is a continuing need for simple and inexpensive injection devices able to assist the user in the various handling steps involved, preventing or ameliorating mistakes and offering an ergonomic, convenient and non-traumatic product, especially useful for patients under self-administration. Although the present invention may have a more general utility, it will mainly be described against this background.
A main object of the present invention is to avoid the disadvantages of known injection devices as described. A more specific object is to provide an injection device able to assist the user in proper performance of all or most operation steps up to and including injection, such as, when applicable, chamber mixing, de-aeration, dose selection and ejection of single or repeated pre-determined doses. Another object is to provide a device assisting the user in securing a proper sequencing of such steps. Still another object is to provide a device being mechanically programmed for proper sequencing. A further object is to provide a device with improved dose setting properties and suitable for delivery of varying doses. Yet another object is to provide a device usable for single or multiple controlled ejections from a container. Another object is to provide a device compatible with pre-filled syringes of various natures. Still another object is to provide a device suitable for self-administration. A further object is to provide a device convenient to handle. Yet another object is to provide a device having few and simple parts, yet giving high operation safety and precision. Still another object is to provide a device easy to manufacture and assemble. Another object is to provide a simple device of low cost, usable as a disposable device. A further object is to provide methods for operating the devices as described.
These objects are reached with the device and method having the characteristics set forth in the appended claims.
By use of a program arrangement based on a system of cooperating tracks and track followers several objects are met. An overall simple design is possible, which can be implemented in low cost parts. It also allows high flexibility in part selection for the cooperating parts and few components are needed if placed on the standard syringe parts, such as housing and piston rod construction, and even so a track can be arranged either on one or the either part, with the follower on the opposite, or a combination thereof for highest program flexibility and for allowing secondary considerations, e.g. in respect of strength and manufacture. The system can be used to positively urge the user into one action sequence only and can even be made irreversible by use of one-way structures. Yet the system is also compatible with reversible action at selected points in the sequence, e.g. when setting the dose, by simply allowing two-directional relative track and follower movements or such movement in an endless loop, e.g. around the device circumference. It is compatible with both axial and rotational movements, and combinations thereof, and can serve to give force or speed transformation, such as in a screw-threaded track, e.g. high force for piston break-loose and low speed for cautious mixing. Use of several track parts branching off from a common track part makes it possible to select one of several programmed paths, e.g. for setting variable doses. Guided multiple dosing systems are offered, e.g. by extending track parts into consecutive axial and transversal parts, optionally with repeated branching to create multiplied alternatives. This with maintained option of combining with a common program part, e.g. for initiation steps with compulsory change therebetween, including de-aeration and unification movements for multiple chamber containers, the latter with option of combining with screw-threaded track parts, as known per se. The system can be divided into more than one track and follower parts, if arranged so that the parts do not counteract, for further program flexibility or design freedom, e.g. with consideration to device size, strength, manufacture etc., or to allow for different characteristics in the various program phases, e.g. several followers for mechanical rigidity in phases not requiring many alternatives, such as initiation, whereas a single follower can be used for phases requiring several alternatives, notably dose setting, for full utilization of available surface for program structures or indicia. It should be noted that in spite of the multitude of functions possible the device can be extremely simple and in its most extreme form the entire track system can be molded or pressed into one surface, e.g. the piston rod outer surface or the hosing inner surface with the follower point structures on the opposing surface, requiring no more than minimum parts. This in strong contrast to prior art devices, which typically require multiple parts already for dose setting, offers multiple ejections only of one dose or requires additional reciprocating parts, use different mechanisms for multiple chamber mixing and often neglect or and leaves to the user the problem of de-aeration and pre-ejection. The simplicity provided meets the objects of device low cost, small size and suitability for disposable design. It also meets the objects of easy manufacture, assembly and compatibility with various container designs. The complete programming and few movements required meet the objects of safety, convenience and suitability for use in patient self-administration.
Further objects and advantages will be evident from the detailed description of the invention hereinbelow.
In the absence of explicit statements to the contrary, as used herein expressions like xe2x80x9ccomprisingxe2x80x9d, xe2x80x9cincludingxe2x80x9d, xe2x80x9chavingxe2x80x9d, xe2x80x9cwithxe2x80x9d and similar terminology shall not be understood to be exclusively restricted to recited element but shall be understood to allow for the presence of further elements as well and shall be understood to cover any element in integral, subdivided or aggregate forms. Similarly, expressions like xe2x80x9cconnectedxe2x80x9d, xe2x80x9cattachedxe2x80x9d, xe2x80x9carrangedxe2x80x9d, xe2x80x9cappliedxe2x80x9d, xe2x80x9cbetweenxe2x80x9d and similar terminology shall not be understood to cover exclusively direct contact between the recited elements but shall be understood to allow for the presence of one or several intervening elements or structures. The same applies for similar expressions when used for description actions.
The injector described herein may be used for a variety of purposes within and beyond the medical area and for any type of preparations, such as chemicals, compositions or mixtures, in any container and delivered for any purpose. For reasons outlined the system have certain special values in connection with medical delivery devices where also the design constraints are more severe than in most other applications. For convenience the invention will be described in terms of this application.
Normally the material to be delivered is a fluid and preferably a liquid, including materials behaving as liquids such as emulsions or suspensions. These observations relate to the final preparation whereas other components, notably solids, may be present before final preparation. The nature of container content shall also be understood to include medical in broad terms and to embrace for example natural components and body fluids pre-filled or drawn into the container although most commonly the medical is factory prepared. Although the principles of the invention are mainly described with respect to ejection they are equally applicable for aspiration steps.
The containers usable in the present injectors generally comprises a container for the preparation and an opening through which the preparation can be delivered and a broad range of container types are useful. Syringe type containers are preferred for use in the present injector and shall be understood in broad terms and can generally be said to include a barrel having a front part and a rear part defining a general axis, an outlet for the preparation, typically comprising a liquid in broad sense, arranged at the front part and at least one movable wall arranged at the rear part, a displacement of which wall causes the preparation to be moved towards or expelled through the outlet. Barrel shape and movable wall have to be mutually adapted. The barrel of for example glass or plastic may have a substantially constant internal cross-section, with a similarly constant barrel axis, between front and rear parts giving a generally tube-shaped barrel, and most preferably the cross-section is of the common circular type giving a substantially cylindrical barrel. The movable wall is then preferably a substantially shape-permanent, although possibly elastic, body sealingly adapted to the internal barrel surface and preferably of the piston type. Depending on the use purpose for the injector, at the outlet a needle, a cannula, an infusion tube or a similar delivery may be in fluid connection with the opening, e.g. by being arranged on, at or with a conduit to the opening. Within these limits and preferences a broad range of syringe type containers can be used with the present injector device, such as ampoules, cartridges, carpoules and syringes. It is also within the spirit of the invention that the container is not a separate part from the housing but that the housing integrally comprises the container although in most instances it is preferred that the container is a separate part. The container need not have a separate plunger but it is preferred that the piston rod to be described can act more or less directly on the container movable wall, although it is fully possible that the container has a plunger, in the sense of a part protruding from barrel rear end, on which the injector piston rod can act for movement of the piston, since many standardized devices are so designed. The injector can with preference be used with standard container types, e.g. as defined in DIN and ISO standards. Also usable are dual or multi chamber container types, known e.g. for preparations demanding a mixing of two or more components or precursors before administration. The components are kept separated by one or more intermediate walls of different known designs, which walls divide the barrel into several chambers, sometimes placed parallel along cartridge axis but most commonly in stacked relationship along the axis. Unification of the components may take place by breaking, penetrating or opening a valve construction in the intermediate walls. In another known design the intermediate wall or walls are of the piston type and flow communication between the chambers is accomplished by moving the piston to a by-pass section where the interior wall has one or several enlarged sections or repeated circumferential grooves and lands or piston deforming structures in a manner allowing by-flow of rear chamber content into front chamber at displacement of the rear movable wall. For the present purposes it is preferred to use multiple chamber designs where mixing can be achieved by an axial movement of the piston rod, either a straight axial movement or a screw movement as known per se. The chambers may contain gas, liquid or solids. Generally at least one liquid is present. Most commonly in pharmaceutical applications only two chambers are present and typically contains one liquid and one solid, the latter being dissolved and reconstituted during the mixing operation. For these types of containers it is possible both that the mixing or reconstitution step has already taken place when the container is placed in the injector or that means are provided within the device for unifying the chamber contents before the actual injection process is started.
As used herein positional and directional statements shall be understood with reference to the container. The xe2x80x9caxisxe2x80x9d or xe2x80x9caxialxe2x80x9d direction refers to the axis along which the container barrel has substantially constant cross-section. The xe2x80x9cfrontxe2x80x9d refers to the barrel end having the opening for content flow and xe2x80x9cforwardxe2x80x9d to directions from the barrel side towards the opening and xe2x80x9crearxe2x80x9d and xe2x80x9crearwardsxe2x80x9d to the opposite end and direction. xe2x80x9cTransversalxe2x80x9d refers to a direction perpendicular to the axial direction and includes xe2x80x9crotationalxe2x80x9d movements around a line parallel or concentric with the axis. Unless otherwise indicated use of the directional statements, such as xe2x80x9caxialxe2x80x9d or xe2x80x9crotationalxe2x80x9d shall not be understood to be restricted to purely the indicated direction but shall be understood to incorporate everything having a component in the indicated direction.
The injector device comprises a housing, which shall be understood in broad sense as long as it performs its basic functions of supporting the container and having, or providing support for, the track or follower structures to be described. The container may be movably arranged with respect to the housing, e.g. to allow initiation steps under movement relative the housing such as under mixing of mixing of multiple chamber containers as known per se, although for the present purposes it is preferred to perform even such steps with the container stationary with respect to the housing. Unless otherwise indicated the container shall be assumed to be stationary, at least in the axial direction, with respect to the housing. The container can be attached to the housing in such a manner that it remains exposed, although it is preferred that the housing also confines the container. The housing should leave exposed parts operated by the user, notably the piston rod when manually operated and for example needle attachments. As indicated it is often preferred to use the device as a disposable in which case it is preferred to factory load it with the container and a simple closure arrangement is of value for rational assembly in manufacture. In broad terms the housing shape is not critical for the basic function of the device but may influence its ergonomic and convenience properties and as common in the art the housing may have a design facilitating it manipulation, such as finergrips and other grip surfaces. Otherwise the overall shape of the housing can take a variety of shapes depending on among others the internal component layout. The housing may be a single or multiple piece part although it is preferred to design it with as few parts as possible. Preferably housing parts are made from plastic material by for example moulding.
The injector comprises a piston rod, which shall also be understood in a broad sense as long as it performs its basic functions of being able to displace the movable wall and having, or providing support for, the track or follower structures to be described. The piston rod need to be movably arranged in relation to the container and is preferably also movably arranged with respect to the housing. It should at least be movable in the axial direction but in order to increase the program design freedom it is preferably also movable in the transversal direction, preferably by being rotatable, preferably around the container axis. Generally the piston rod comprises a penetrating part designed to penetrate into the container barrel and preferably also have an accessible part remaining outside, e.g. providing access for manipulation. The piston rod can be moved by an actuator system incorporating stored energy, e.g. by springs, compressed or generated gas or electric motor means, but when simplicity is important it is preferred to design the piston rod for manual actuation for which the principles of the invention are also well suited. The track and follower structures can be arranged on different parts of the piston rod, a track even on the penetrating part whereas a follower preferably is arranged on an accessible part. When essential parts of the track are arranged on the piston rod it has been found beneficial to provide for a large surface on the piston rod, e.g. by making the penetrating part as large as the barrel size allows. A preferred way to increase the available surface is to enlarge the accessible part of the piston rod, which part in principle can be made as large as required in length and width, which has the additional advantage of allowing small containers, and to locate track parts to these enlarged surfaces of the piston rod. The enlarged surface can be arranged axially rearwards of the penetrating part but it is preferred that it extends axially forwards to at least partially extend over the container barrel outside when the penetrating part moves into the barrel. Preferably the penetrating part and the extended part run at least partly in parallel to accommodate the barrel therebetween. Most preferably the extended part of the accessible part has the overall shape of a tube or sleeve concentric with the penetrating part. The general layout described gives manufacturing and rigidity advantages in addition to the track structure benefits. Also the piston rod can be designed as a multipart piece although it is preferred an possibel to make it as a single piece. Preferably the piston rod is molded in plastic.
Tracks can be provided on either a housing part, a piston rod part or on both. The followers shall be arranged on the opposite housing or piston rod part, having the track with which it arranged to cooperate. For purpose of track system description, any other injector part, such as an intermediate part, shall be regarded as part of the housing or the piston rod respectively depending on its functional relationship thereto, mainly with which part it moves. Tracks can be arranged on the housing, for example on the housing interior surface or as slits in the housing wall, with one or more followers on the piston rod, which for example allows for a slim device. It is preferred to place tracks on the piston rod with one or more followers on the housing part, which among others allows for rigidity, ease of manufacture and flexibility in track layout. It is possible to place tracks on both the housing and the piston rod although it is generally more advantageous to have tracks only on one of the parts.
The physical implementation of the tracks can take a variety of forms. The track may be a raised rail gripped by a correspondingly shaped follower. Especially in thin materials the track may be a slit. Tracks in the form of grooves are generally preferred among others for rigidity and ease of manufacture. Such a groove may have cross-section for example being concave, rectangular or with undercut, e.g. for catching a correspondingly shaped follower. The tracks in general preferably having constant cross-section over a certain extension corresponding to at least several times their width and may be so in their entire length but it is also possible that the cross-section changes, for example at a knee or bend, e.g. to accommodate an asymmetrical follower, which may be used to meet different space or strength limitations in different directions. Mostly it is preferred that the track guides the follower line movement only, which need not and most often is not straight, so that movements away from the line are prevented. The track may, however, also widen or disappear at certain locations, e.g. to release a follower for example when another follower is engaged, to allow several movements or where a guided movement is not necessary. In such situations the line guidance of the follower can be said to widen into an area. Another similar situation is when it is only necessary or suitable to guide the follower movement against dislocations towards one of the lateral sides of the track, e.g. when dislocations to the other side is prevented by other means for example a second track or follower, when a pumping action is allowed or to allow entrance of a follower into the track from more than one or numerous positions. The track may then be reduced to a one-sided track, e.g. an edge.
Also the followers can take a variety of shapes. The follower can basically be regarded as a xe2x80x9cpointxe2x80x9d structure able to pass along the line or area provided by the track and should have physical dimensions slightly less than the track parts to be passed, except where friction controlled elements are arranged to be described. It can with preference be symmetrical, e.g. have a round or square cross-section when seen perpendicular to the track plane. The follower may, however, also be asymmetrical, e.g. longer than wide, when only unidirectional movements are needed or even in multi-directional tracks if the track changes cross-section when it changes direction to accommodate the new width of the follower or if the follower is movably, e.g. rotationally attached to its substrate, which also can be used to allow adaptation to threads of varying pitch. The follower cross-section when seen along the track may be adapted to the corresponding track cross-section although it is not necessary and sometimes a non-congruent shape is preferred, e.g. giving point rather than surface contact between track and follower for reduced friction. The follower may also be movable in a direction substantially perpendicular to the track carrying surface, e.g. to allow engagement or disengagement with the track, preferably biased in one direction by spring or material resilience, for automatic or manually assisted control. In the later case, the follower is preferably arranged on the housing.
Any track can have additional control elements as known per se, such as one-way structures, facilitating follower movement in one direction in the track but preventing movement in the opposite direction, e.g. in the form of a hinged stop surface yielding only in one direction or a structure having a ramp surface in the forward direction and a steeper stop surface in the other. Alternatively a follower movable towards the track surface as described can be arranged to require an operator action before further movement is possible. Also any track can have tactile structures where a change in resistance takes place, for example to alert the user at critical points in the process or to bias the follower into predetermined positions such as when aligned with a continuing track part. Optionally the tactile structure also provides an audible click confirmation. Grooves or ridges in the over the track or the abovesaid one way structures can be used for this purpose.
As used herein xe2x80x9ctrack systemxe2x80x9d refers to the total arrangement of tracks and followers in the device. For purposes of description the track system will often be described as comprising different tracks, in turn being divided in sections and parts. Such categorization shall not be regarded as binding as a different terminology or categorization gives the same functional result. The track system may comprise a single xe2x80x9ccontinuousxe2x80x9d track, in the sense that it can be traversed by a single follower, where cooperation with the follower assists in various operational phases. Preferably the track system incorporates more than one continuous tracks cooperating with at least one follower each. The two or more tracks may then be arranged in xe2x80x9cparallelxe2x80x9d, meaning that over at least part of their operational range they are arranged to allow the same movement of the piston rod, which may be used to increase guiding rigidity and precision or to allow a smaller or slimmer device with maintained rigidity and precision. A threaded track for example may have two or more parallel threads with followers. Preferably the track system incorporates at least two xe2x80x9cserialxe2x80x9d or xe2x80x9cseriallyxe2x80x9d arranged tracks, meaning that the tracks are arranged for guidance of the piston rod into different movements, either in true series or enabled by engagement/disengagement of follower, which may be uses for larger design freedom or to adapt the track and follower characteristics different for different operational phases, e.g. parallel tracks followed by a single additional serial track allowing utilization of the full circumference of the device. Another advantage is that serial tracks normally allows a more compact track system layout, e.g. less axial extension. Normally serial tracks requires the first follower to go out of engagement when the second follower goes into engagement with its track. The disengagement can be made by letting the first follower leaving its track entirely, i.e. by having an xe2x80x9copenxe2x80x9d termination, by going from a line to an area guidance as described, by allowing multiple line guidance alternatives for the first follower corresponding to all movement options for the second follower or by use of movable followers as described.
General control features of the tracks are to provide either a stop for a piston rod movement or a change of its allowed movement direction. A permanent stop at a predetermined location or distance can be provided by giving a track a xe2x80x9cclosedxe2x80x9d termination, i.e. the follower has no further movement alternative than possibly to go back. Such a permanent stop may be used at the end of the operation cycle, for example when the ejections programmed for are completed. The follower may then be allowed to move in the opposite direction in the same track, for example to permit re-filling of the container or it may be prevented therefrom, e.g. by a one-way structure behind, for example to block a disposable device from further use. In most other situations a stop for a running piston movement is preferably not permanent but combined with new movement options for the piston rod. The stop is then preferably provided by a track wall where the track changes direction, preferably at a sharp change and most often at a substantially right angle to the current track part, e.g. at xe2x80x9ckneexe2x80x9d, giving the follower only one new movement alternative, or at a xe2x80x9cbranchxe2x80x9d, giving the follower at least two new movement alternatives, preferably so that a change in piston rod movement is needed before a new movement alternative can be reached.
Track directional changes may be combined and repeated. If for example multiple knees are combined a xe2x80x9cstaircasexe2x80x9d track shape can be provided if each second movement is made in the same direction and a xe2x80x9cmeanderingxe2x80x9d track shape can be obtained if each second movement change is made in opposite directions. If some or all of the knees are replaced with branches a xe2x80x9cgridxe2x80x9d track shape is possible, allowing more than one movement option in each grid intersection, creating multiple combined alternatives. The multiple directional changes described can with preference be used in multiple dose systems, preferably so that the track provides several axial sections combined with intermediate transversal and preferably rotational movement sections, whereby the user experiences a definite stop at the end of each dosing with the requirement for an active directional change. The axial sections can be of different lengths but it is preferred in most instances that the axial sections are of about equal lengths in each track to provide repeated equal doses, possibly with exception for the first axial part, which may be used to force the user making a de-aeration step of pre-determined volume and/or to initially discard content volume not to be used, and normally these volumes are different from the dosing volumes. Most preferably the equal axial parts represent an integer division of the whole container content and when several tracks are arranged for they may provide different integer divisions of the total volume. The transversal section can also be given varying length, e.g. larger than one track width, shorter than two track widths if the stop surface is sufficient, normally at least two widths but can be longer but preferably less than the available circumference. Space considerations may be determining but also e.g. positioning of readable scales or indicia, for which purpose small transversal movements may serve to keep axially arranged characters within trail of window limits and large transversal movements may serve to bring large characters out of a windows and new in. These considerations also apply for transversal movements in single dose applications.
While axial piston rod movements generally performs an active function on the container content, rotational movements may be used for other purposes. One such purpose have been indicated above in multidose arrangements where rotational movements are used to assist in stopping one dose operation and requiring an active step before a new dose can be delivered. A further preferred purpose of a rotation track is to allow for selection between several axial tracks branching off from the rotational track, which then preferably may be designed in ring form, either at least partial ring form with closed termination to permit only reciprocating movements or preferably as a complete ring allowing full rotation of the follower therein. A third preferred use of a rotational track is to allow for a screw-threaded movement of the piston rod, performing both an axial and a rotational movement, which may be used for known purposes, e.g. change of speed or force ratio to eject small controlled volumes, high viscosity products or perform controlled reconstitution of multiple chamber containers, as known per se. The thread may extend only partially over a complete revolution, e.g. for ejection of small volumes, up to several turns, e.g. in reconstitution. It is fully possible to use threads of varying or pitch if the follower is designed accordingly, as indicated above. Generally rotation is made around a line concentric with the container axis.
A preferred use of ring track is as a joining track for several tracks branching of from the ring track and running at least partially in the axial direction. This layout can be used to provide for different track programs for differences in container type, container content type or patient requirements. Especially the layout is useful as a dose setting arrangement for a given container. The ring track should preferably provide for a line guidance of the follower, either by itself or in combination with a second track, as any uncontrolled axial movement of the piston rod may result in a dosing or initiation error or create uncertainty with the user. Dosing, or expelling, tracks branching off from the joining track and running at least partially in the axial direction, preferably for forward movement of the piston rod when moving from the joining track to the dosing tracks, may be of the general types outlined above, i.e. being arranged for single or multiple ejections. It is preferred that at least two, and preferably all, of the tracks are different, preferably by providing for different stroke lengths.
It is also preferred to arrange for readable dose indications in connection with dose selection arrangements. Generally the program provided forces the user into a single chain of sequential actions without alternatives but in connection with dose selection several alternatives are necessarily present and, although indications can be used in any phase, preferably indications are used for guidance in the dose selection phase. This can preferably be done so that indications or characters on one of the piston rod or housing parts are shown in a window, or pointed to by a pointer, on the other part. The characters may be positioned in a ring parallel to the joining track, e.g. on surfaces between the dosing tracks to conserve axial space or on a ring area free of dosing tracks, preferably to the rear of the dosing tracks, to enable use of larger characters.
It is also preferred to arrange for guided initiation steps in connection with this layout and in particular to provide for a controlled de-aeration step. As used herein de-aeration shall be regarded as including the possibility of pre-ejection of liquid, which in turn shall be understood to include discarding of liquid not to be used, which is an alternative known way of performing partial single dose ejections. De-aeration can be arranged for by providing each of the dosing tracks with an initial part, adapted in axial length for the de-aeration step, followed by a transversal part before the actual axial dosing part. Preferably the initial part for the different dosing tracks have about the same axial length, unless used for discarding, whereas the dosing part of the tracks preferably are different and preferably longer than the initial part. Another preferred layout, especially when discarding is not included in the de-aeration step, is to arrange an initiation track in the process before the joining track, so that the de-aeration takes place before the dose is selected, which gives a proper action sequence, necessitates only one initiation track for all dosing tracks and automatically gives the same initiation length for all the dosing tracks. The initiation track should run an axial distance suited for de-aeration and preferably land on a stop surface to require an active directional change for dose track selection. Preferably the stop is a wall of the joining track not allowing entrance to any dosing track, e.g. between such entrances. The initiation may include other process steps than the deaeration and preferably then is preceded still earlier by a mixing track for multiple chamber containers. Such a track can be substantially axial, e.g. straight and terminated with a knee or branch, but is preferably screw-threaded as known per se, and may contain several parallel thread tracks with several followers as generally described above.
As indicated above a screw-threaded track, with constant or varying pitch, may be used for several purposes of which not all need any additional actions after the screw movement, for example when the movement is used for final ejection of small or high viscosity doses. In contrast, when used for multiple chamber reconstitution most process steps comes later in the cycle and it is desirable to provide a track system integrating these demands and in particular such a track system incorporating multiple dosing since multiple chamber systems frequently are designed to result in multiple doses after mixing, which hitherto has required complicated injector mechanisms. Hence a preferred track system layout incorporating screw-threaded tracks is to incorporate also a track for multiple dosing, e.g. any of the general types outlined above such as of staircase, meandeing or grid type with only one or several selectable tracks. In order to enable this it is preferred to provide a joining track of the general ring type described above and let the threaded track continue directly into the joining track, which is possible with only a small directional change, the magnitude of which depends on the thread pitch. With the follower in the joining track all the optional alternatives described in relation the branching layout described above are available, especially for selection of several continuing tracks. Another preferred alternative is to let the thread track continue substantially in the axial direction, whereby the user will experience a stop for the threaded movement indicating that an axial movement is now necessary. The axial track part may be the entrance of a dosing track for single or preferably multiple doses as described. Preferably, however, the first part of the axial part is a de-aeration track, running a length adapted for this purpose, which may then continue in a knee or branch for single or multiple selection dosing tracks respectively, which dosing tracks in turn may be designed for single or multiple sequential dosing. The axial length of the de-aeration track is preferably different from the axial length of the dosing tracks, which in turn may be individually different but when of multiple dose type preferably each has repeater dosing sections of equal axial length. The arrangements described are fully compatible with two or more parallel tracks, having at least one follower each, e.g. by parallel threads continuing into parallel de-aeration tracks and parallel dosing tracks.
The above layouts have been described as if composed of continuous tracks in the sense that they can be traversed by a single follower. It is fully possible to modify the layouts to instead use two or more serial tracks as with corresponding advantages as generally described earlier. A preferred use of serial tracks is to use a first track with first follower, or preferably two or more parallel first tracks with first followers, for initial steps in the cycle, preferably mixing step and/or de-aeration step and most preferably both whereas a second track with a second follower for dose setting and actual ejection or ejections, the first and second tracks with respective followers being arranged as serial. The initial steps may not require selection among several track alternatives but instead may require parallel tracks and several followers of high rigidity and precision for the extended piston rod extended in the early phases. The dose selecting step instead may require substantial surface and full utilization of available circumference for the several tracks and possible information display to the user. Use of serial tracks solves this problem and in addition permits a compact track system layout. The followers may be arranged on the same part for both of the serial tracks, i.e. on either the housing or the piston rod, e.g. for simplest layout, or the first tracks may be arranged on one of the parts and the second track on the other part, e.g. to increase available surface for the track system and allowing for example tracks on axially overlapping parts. It is possible to perform disengagement of the first followers and engagement of the second follower or followers by a rotational movement, e.g. with exits and entrance respectively for example arranged in a bayonet type arrangement, but it is preferred that follower disengagement and engagement takes place by an axial relative movement between track and follower, especially so that the disengagement and engagement take place at rear and front parts respectively of the part having the track system. In other respects the first and second tracks can be of the general types earlier outlined, e.g. a straight or preferably threaded track for mixing, a straight axial track for de-aeration and a ring shaped joining track for dose selection, branching into several single or multiple ejection dosing tracks.
The above description has been made with reference both to structural and operational features, directly or indirectly, or follows from the descriptions made of structures, functions and objects. The invention shall be regarded to incorporate and embrace both the device and method aspects and characteristics described. The methodological aspects are not separately repeated. It should be pointed out, however, that all layouts described are compatible with the crucial step of securing de-aeration of the container before ejections are made, a step often neglected although important to positively guide during operation, especially at self-administration. A method for securing this operational phase may include the steps of a) displacing the piston rod forwards in a movement having at least a component in the axial direction, performing hereunder de-aeration and/or pre-ejection of the container content, b) rotating the piston rod in a direction different from that of step a), and c) advancing the piston rod forwards in a movement having at least a component in the axial direction, performing hereunder ejection of container content. During the de-aeration step the user should preferably hold the device so as to secure flow of container content from below and upwards, preferably by pointing the container opening at least partly upwards. Any other method step as described may be added.
In other aspects the injector of the invention may be used conventionally or as described in prior art. Below a summary of preferred actions. If the container is not preassembled in the device housing the operator inserts the container and possibly connects it to attachments provided and assemble parts involved. If the container is a dual or multiple chamber device mixing operation may be undertaken before attachment to the device but is preferably made when attached as described. Unless a needle, infusion tube or other delivery unit is already in place the operator may mounts such a device on the container opening and possibly removes any needle shield present. The opening is pointed roughly upwards and the movable wall is moved forward to expel air and possibly eject a small preparation amount to assure proper function. Preferably the wall is moved forward by disclosed herein. If applicable a dose setting operation may take place by any of the methods described. If applicable the device is moved so as to perform a penetration movement to bring the needle into a target object, e.g. human or animal tissue or any other material or device. One or more ejections may now be performed by any of the means and methods outlined. Finally any penetrating device may be withdrawn from its target site.